Method of protecting conduits projecting into filled areas



Patented June 15, 1926.

UNITED STATES PATENT oFFICE.

-ANSON MARSTON, OF AMES, IOWA, ASSIGNOR TO 10V/'A STATE COLLEGE OF AGRICUL- TUBE AND MECHANIC ARTS, OF AMES, IOWA, A CORPORATION OF IOWA.

METHOD OF PROTEC'IING CONDUITS PROJEGTING INTO FILLED AREAS.

Application filed September 12, 1924. Serial' No, 737,370.

When conduits of concrete, tile or other material are laid in ditches, and the ditches lilled with earth, the'subsequent settling of the earth lill subjects the conduits to such strains only as are applied by reason of part of the weight of the earth in the ditch above the conduit. When, however, these conduits are laid on or only partly below the ground lsurface and 'then a lill ofconsiderable depth isvplaced on top of them, then as the earth settles the conduits will be subjected to y strains due not only to the weight of the earth immediately above the conduit, but also to art of the weight of' the adjacent earth lill? The reason that, under such conditions, the conduits are subjected to anV additional crushing strain is the fact that the conduits themselves are relative-ly incompressible, so that the earth lill alongside moves downwardly in settling to a greater extent than the earth immediately above the conduit, with the result that part of the strains or pressure due ,to settling of the earth lill at the sides of the conduit are applied to the top of the conduit, by reason of the adhesion of the earth at the sides of the conduit to the earth immediately on top of the conduit. In my experiment-s I have found that the total load onV the'conduit frequently is doubled, or even more than doubled, in this manner.

My object is to provide an inexpensive method which may conveniently and easily be practiced in any locality and with materials that are inexpensive and readily obtainable in any locality, whereby a conduit laid projecting into a filled area will be subjected to suchstrains only as are occasioned by :a part oi the weight oli' the earth lill immediately above the conduit, and will not be subjected to additional. crushing strains from the body ot' earth lill alongside.

My invention consists in the various steps of the method by which the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my' claims, and illustrated in the accompanying drawings, in

which:

' Figure l showsa sectional view of a conf duit resting upon solid earth and having an earth fill of considerableV height above it. In this ligure I have illustrated the manner in which my method maybe practiced, which consists in loosening successive layers of earth lill directly above the'conduit after the layers have settled.. i

Figure 2 shows a similarrview illustrating another embodiment of my invention, which consists in providing movable frames at the sides ofthe culvert which may be raised Jfrom time to time as the lill progresses.

Figure 3 shows a similarv View illustrat ing an embodiment of my invention in which I utilize a material which is capable of settling much more readily and extensively than the earth fill at the sides thereof; and in Figure t I have shown a moditicationof this embodiment of my invention which consists in employing vertically separa-ted layers of readily compressible material above the conduit. A

Referring to the accompanying drawings, I have used the reference numeral 10 to indicate the solid earth upon which the conduit l1 is'permanently located.

In the form of my invention illustrated in Figure. 3, I have used the reference numeral.

12 to indicate the ordinary earth till in the area into which the conduit projects. Immediately on top ofthe fconduit, I have placed a lill which may be of straw or the like, and which is indicated by the reference numeral 13, and is capable ct settling to a much greater degree than is the earth lill 12 surrounding it.

In practice I have found that it is necessary to provide this lilling material 13 only for a fraction of the distance upwardly from the culvert, and then above it the area may be lilled with the earth material l2 in the ordinary way.

In the modification illustrated in Figure 4f, I have provided a series ofl layers ot readily compressible filling j material i3 spaced vertically onel above the other and all .in layers steve tendait. In prestige With this modification, the earth is filled to a point nearly level with the top of the conduit. Then a layer of highly compressible material 13 is placed on top of the conduit. Then a layer of earth is filled in over the material 13 and over the fill at the sides of the conduit. Then an extra layer of highly compressible material 13 is placed on top of the last mentioned fill, and so on.

In the form of the invention illustrated in Figure 1, the earth fill indicated by the section lining 14 is completed to a` point not very far above the top of the culvert with material compacted by the method of construction or by time to such extent as may be practicable. Then the material 15 immediately above the culvert is spaded or plowed or otherwise loosened. Then a second layer 16 of filling material is placed throughout the area` of the fill and over the conduit, and this layer likewise is compacted to such extent as practicable. Then the portion 17 of said layer is loosened in the same manner as the portion 15 before described just prior to the time the third fill is made and so on.

In the modified form shoivn in Figure Q, I provide movable frames 18 with opposite sides vertically over the sides of the conduit and spaced apart by the brace 19 and extended a short distance above the conduit. The first layer of filling material 20 is applied over the entire area to be filled except the area Within the movable frames 18 and then is permitted to settle, unless already Well compacted by the method of making the fill. After this is done, the area within the movable frames is filled with very loose material, using precaution against compacting, after Which the movable frames 18 are raised to the position shown by solid lines in Figure 2. Then a second layer is filled over the area outside the movable frames and permitted to settle, and so on.

I have demonstrated by Xperiment that the ordinary large conduits are seldom made strong and rigid enough to resist such strains as are applied to them when they are placed on the solid earth and the entire area over and around them is filled with a considerable depth of earth, which subsequently settles, and by repeated experiments and tests I have found that even when placed in a ditch which is subsequentlyv filled, there is practically no breakage or cracking of a conduit, yet if the same conduit projects into a lled area, a. very great amount of breakage and cracking of the conduit is occasioned after settling.

I have also demonstrated by experiment and test that in the case of conduits projecting into lled areas, strains to which a conduit is subjected upon settling of the filled material, include strains caused by the Weight of the material directly above the conduit, and in addition part of the weight of the filling material alongside. The amount of filled material, the crushing Weight of which is thus thrown upon the conduit, depends to a great extent upon the nature of the material, its degree of adhesion and the extent of the projection of the conduit into the filled area. In extreme instances, I have found that the crushing strains upon the conduit projecting into a filled area are several times more than the crushing strains upon a corresponding conduit laid in a ditch.

lhen my improved method is employed, for instance the method illustrated in Figure 3, the earth is filled up to a point near the top of the conduit and then directly above the conduit I place a layer of readily compressible material, such for instance as straw. This need extend only a fraction of the distance to the top of the fill. Then When settling` occurs, the material at the sides of the culvert can settle down to its normal. condition. The straw fill will settle more readily and to a greater extent than Will the earth fill at the sides. Hence, none of the Weight of the material atthe sides of the culvert Will have been thrown upon the culvert proper. In fact part of the Weight of the earth fill immediately over the conduit will be thrown upon the filling material alongside, leaving the conduit to carry only a fraction of said Weight of the filling material immediately overhead.

In localities Where it is impractical or too expensive to obtain a highly compressible material, such as straw, I have found that I can obtain satisfactory results by filling the material in layers, consolidated to such extent as may be found practicable, and then spading,.plovving or otherwise loosening the filled material directly above the culvert, and continuing this method during the successive layers of fill material.

In the modified form illustrated in FigA ure 2, the movable frames permit the attainment of such loose. condition of the filling material immediately over the conduit uithout subsequent spa-ding or plowing or other loosening process.

I claim as my invention:

1. A method of protecting conduits projecting into filled areas, which consists in placing directly above the conduit a material having a greater degree of compressibility due to settling than that of the filling material alongside.

2. The method of protecting conduits projecting into filled areas, ivhich consists in placing a filling material in layers compacted as `far as practicable, and then loosening the material that lies directly above the conduit so that it shall have a greater de` gree of compressibility than that of the inaterial alongside.

3. The method of protecting conduits proteria-l outside yof the frames to Settle 0r pack jecting into filled areas, which consists in to a. greater extent than the material be- Y placing movable frames at the sides of the tween the sides of the frames, than elevat- 10 conduit, then filling in materiel against the ing the frames and continuing the process 5 outer surfaces of said movable frames and until the lill is completed.

also between the sides of seid. movable frames, then permitting or causing the me- ANSON MARSTON. 

